I may be wrong but I see comparing Banff to Collingwood/Wasaga Beach as apples to oranges.
They aren't the same, but there is a similar principal at play; serving a tourism niche, and a connection between a major urban centre that is the source of much of that demand and the tourism/resort location. The differences do need to be accounted for though.
Banff is a major, international tourist destination, with a significant number of visitors flying into YYC.
True, though the number of tourists visiting Banff is listed at ~4M per year; while the number of visits to Wasaga/Collingwood/Blue Mountain is ~12M. That set of stats, is, of course, deceptive. As overnight visits and multi-day stays will almost certainly be greater in Banff vs day visits in the Ontario setting.
However, day visits also mean more transportation demand back and forth vs that which Banff would generate.
This means that a significant proportion of the visitors are traveling through YYC and without the train they would need to rent a car.
No question that a much higher proportion of Banff's visitors arrive by air vs the Ontario context; and that a single point of origin is better suited to rail as a rule of thumb.
There is also an existing active rail ROW that can be followed.
(referring to Banff above) Yes, though it is the CP mainline, and therefore would require considerable capacity upgrades.
Correct me if I am wrong, but Collingwood/Wasaga Beach are mostly visited by those who live all over the Golden Horseshoe. That means that people are coming from many different places, so there isn't a fixed origin (a train from Toronto would only serve a small portion of the visitors)
See above
and most likely already have a car.
I wouldn't automatically draw that assumption in the GTA. But certainly most
current visitors arrive by car.
There is a need there to separate potential market vs current market.
Also, there is no longer an active ROW rail that they can follow (though there may be an abandoned one).
There is an active ROW for a portion of the route, which is in poor condition and would have to be refurbished/replaced. There is an inactive, but largely in tact ROW most of the rest of the way; though there is no ROW right to the points of peak-interest. So that would either require spur construction or an alternative last mile link by bus.,
It also seems to me as if Banff is a destination that you can get away without a car more easily at than Collingwood or Wasaga Beach (though I could be wrong on that one).
I don't think I would draw that conclusion. If one is going to Banff, unless you're staying at a hotel/resort, you will need transportation to get to hiking trails in summer or ski hills in winter.
Where many Wasaga Beach go'ers would spend most or all of their day on the Beach; and skiers would spend their day inside the Blue Mountain Resort w/o need for a car.